By Peter Henderson

INVERNESS, California (Reuters) - In the famously liberal and prosperous enclave of Marin County, California, environmentalists and local food fans usually line up on the same side of any given cause. The oyster, however, has managed to cleave them far apart.

The U.S. government sided with environmental groups on Thursday with its decision to shut down a 40-year-old Northern California oyster farm in an attempt to restore wilderness.

Secretary of Interior Ken Salazar said he would not renew the lease for the weatherbeaten shacks, oyster shell mounds and waterlogged docks that make up Drakes Bay Oyster Company.

The lease ends Friday, and then Drakes Estero in Point Reyes National Seashore, an hour north of San Francisco, will be turned into the West Coast's only designated marine wilderness outside Alaska.

Harbor seals, birds and native grasses are expected to reclaim the property, four decades after a collection of local ranches and oyster farmers agreed to sell their land to the government, rather than developers, in exchange for long-term leases. The Interior Department will renew leases on cattle operations.

Workers on a small dock crowded with oyster crates, a power drill to separate mollusks, and a rickety conveyor belt, cried openly after Salazar called owner Kevin Lunny in the morning with the news. A third generation cattle-rancher, Lunny took over the oyster company lease seven years ago and had hoped to renew it.

California is wrestling with how to have its wilderness and its freshly grown local food too, issues at the heart of the oyster war. "Sustainable" is the popular catch phrase in the state, adding the notion that food production needs to work long-term - and be profitable - to the "organic" manifesto of chemical-free farming.

But the lofty goals, which fit the bill of high-end San Francisco restaurants, don't go down so well with environmentalists who say there are places one cannot compromise.

'SERIOUS, IRREPARABLE HARM? NO'

Oyster joints, from roadside dives to upscale zinc bars, are thriving in California and Drakes has helped meet demand with 450,000 pounds (204,100 kg) of oyster meat annually. Environmentalists say production from other parts of the state will compensate for the Drakes oysters, but Lunny expects increased supplies from Asia.

Lunny lamented that "we could have had a powerful discussion," about "working landscapes and sustainability" versus "hands off preservation of wilderness." But attempts at that conversation were overshadowed by a bitter fight over the science about whether the oyster farm hurt the estuary.

Sierra Club Deputy Executive Director Bruce Hamilton agreed the fight was unfortunately nasty and the science less clear than either side suggested.

"There is harm," said Hamilton. "Is it serious, irreparable harm? No. But you can't put that many motor boats and that many exotic oysters and not have some harm."

For the Sierra Club, the matter was simple - you can't have an oyster operation in a wilderness.

"National parks are not places where you authorize private use of public lands," agreed National Parks Conservation Association Associate Director Neal Desai, one of the leaders of the effort to end the lease.

OYSTERS LEFT IN BED

His sentiment was echoed in the vast majority of tens of thousands of comments submitted to the National Parks Service.

Plenty of locals sided with the environmentalists, but some were concerned about the loss of tradition, jobs and good food.

"Devastating. Devastating," said Linda Sturdivant, who had been a caretaker for a former owner and said the Lunnys cleaned up "a real dive."

Self-described "treehugger" Todd Board, picking up oysters at the farm store, said that agriculture and environment had to coexist - or the environment would lose. "Of all entities, the Sierra Club is not seeing the forest for the trees," he said.

Salazar gave the oyster company 90 days to pack up. "The Estero is one of our nation's crown jewels, and today we are fulfilling the vision to protect this special place for generations to come," he said in a release.

Out on the dock, the Lunny family was stunned but seemed more inclined to fight than leave, if they could only figure out how. "We're not finished," Lunny told his workers.

His son, Sean, 24, a fourth-generation rancher aiming to become a second-generation oyster farmer, said the slate gray water still teemed with his family's work. "I just know that we have three years of oysters out there," he said.

(Additional reporting by Ronnie Cohen; Editing by Mary Milliken and Eric Walsh)